Qi wireless charger is most likely to be familiar to you because it supports a range of smart phones, accessories and products. The PMA standard, which is now combined with AirFuel, has also appeared in some smart phones, and has also provided charging stations for commercial companies such as Starbucks. These two standards are based on inductive charging technology, usually very short range, and can be quite elaborate. Rezense, the old A4WP standard is based on resonance technology, but this design has not yet appeared in any smart phone.

The coil of the wire generates magnetic field, which can be used to generate current in isolated insulated coil. This is the foundation of transformer technology and induction and harmony charger. The technology based on induction and resonance produces very different results from the point of view of the end user, although the coils can be used for the same engineering principle through air transmission power.

If you are interested in science, the wireless charger uses a tightly coupled coil and has a slight "non resonant" frequency to achieve high transmission efficiency, thus making use of the power effectively, but at the cost of high sensitivity to the alignment of the coil. This is why Qi and PMA devices often use magnets to configure the receiving board equipment and limit the very short charging distance, usually only 45mm.